Insulating a garage - worth it?

I have a detached 2 car garage, stick-built, no insulation, one older metal overhead door, a man door and two small windows. It cooks in the summer time - gets up to an honest 115°, regularly, during the hot months here. I had been planning to insulate/sheetrock the walls and insulate ceiling (but leave the rafters open/accessible for storage), but my parents-in-law have told me they don't think it's worth the hassle, since the door is such a big loss.

Now, I'm not necessarily looking to keep the place 68° over the summer when it's 100° outside, but it's pretty much uninhabitable a couple months out of the year. (I'm leaving out winter concerns since I don't mind the cold too much.) But if I could get the place reasonably insulated, I'd think about popping one of my spare window A/C units in to cool the place off, too.

Seeing as how a brand new insulated door is out of the budget for a while, would I be wasting my time with insulation & drywall for the time being?

Insulate the door too with that pink block stuff. I think it would be worth trying anyway.

I think your biggest bang for the buck is going to be to cross-ventilate under the roof (push/pull fans or ridge vent) and then insulate the ceiling with fiberglass and sheetrock.

Waste of time without the insulated door. Window unit will be OK if you use solar power. On a day like today, my oversized window unit is having a hard time keeping my guard shack cool.

Get a big ass fan. 110 degree days are bearable in a garage with a big ass wind tunnel fan.

Do it. My FIL and I did mine with construction site cast offs and it has made a big difference.

For the door, I used some fiberglass ceiling tiles that I fit into the door panels and they work great.

Big Ass Fans

Yes. Do what you can as it will help. Insulated doors may or may not make a difference depending on how they face the sun.

We insulated most of the walls of the g/f's ~900 ft2 garage with fully insulated 12" ceiling joists. The (2) garage doors (9'wx8'h & 8'x8') were std wood construction with single pane glass. The south/west facing walls are mostly insulated except for the section where the electrical panel is as I'm still working on that. The insulated walls are cool to the touch in the afternoon. The uninsulated wall literally radiates heat. The doors face west and would take the full brunt of the afternoon sun and turn into giant radiators fighting the single window a/c unit (it lost). In this configuration, the garage would stay somewhat tolerable with the a/c on - mainly to take the edge off the humidity - and it really needed to be turned on while the garage was still cool as it simply doesn't have the BTU horsepower to cool a space that large, but did ok maintaining temp for awhile so you weren't be dripping sweat all over whatever you're working on.

The big change occured when the doors were replaced with foam-core insulated doors with dble pane windows last year. Wow. I went out there yesterday afternoon and the inside was still cool. It got hot quickly when I opened the door for awhile to move stuff around, but cooled down a surprising amount after the door was closed again.

You can buy the foam panel sheets used to insulate under exterior wood paneling. Foil on one side, bare foam on the other. can be easily cut to fit in the panels of your garage door. I had a west facing metal door in my last home. Between tinting the windows and the foam panels, there was quite a temperature difference.

First thing I did to my garage when I bought my latest house was to sheet rock all the walls, texture, and paint. I regret not spending the extra time and a few bucks to insulate while I was in there. Luckily San Diego summers and winters aren't extreme enough to be a big issue though.

I put the foam like CJ mentions on the south facing non-insulated metal garage doors on my house in League City, TX. I just cut the panels to fit and glued them up with liquid nails. It helped a lot.

I'd insulate at the rafters, giving you an attic space, which then needs to be fairly well ventilated. Putting ionsulation on the roof won't protect you the same, plus its real hard in shingles.

good ideas in here. i completely forgot about adding insulation to the bare metal garage doors.

of course SWMBO says once the projects in the HOUSE are done, then I can work on the garage .......grrrrr

Also look at seals around the door, insulation won't stop big gaps of cold air blowing in.

Insulating the ceiling without sheetrock is worthless.

You need an air infiltration barrier. Insulation filters the air, but does not prevent infiltration.

Insulation is designed to be used in conjunction with (directly against) an air infiltration barrier. Sheetrock, plywood, styrofoam, cardboard, etc.

Try a reflective heat barrier on the bottom of the roof decking first. If that doesn't do enough, add the insulation at the rafters.

i read the title 'insulting garages'

In reply to madmallard:

Mine's an insult to my projects and aspirations, but I'm working on it.

Need to do more looking into this insulating at the ceiling/joists vs at the rafters... Hoping to do drop-down stairs and store some stuff up above...

Along with all the insulation everyone has suggested, I would drop a solar powered exhaust (pull) fan or two on the roof so it can pull some of that heat out of the garage.

It would also help if you choose to throw the A/C unit in there. It won't take so long to cool it off.

If you do go through with insulating, hit me up. I'll give you a hand.